990,793 research outputs found
Z_2 Topological Insulators in Ultracold Atomic Gases
We describe how optical dressing can be used to generate bandstructures for
ultracold atoms with non-trivial Z_2 topological order. Time reversal symmetry
is preserved by simple conditions on the optical fields. We first show how to
construct optical lattices that give rise to Z_2 topological insulators in two
dimensions. We then describe a general method for the construction of
three-dimensional Z_2 topological insulators. A central feature of our approach
is a new way to understand Z_2 topological insulators starting from the
nearly-free electron limit
Reflections in abstract Coxeter groups
Let be a Coxeter group and a reflection. If the group of order 2
generated by is the intersection of all the maximal finite subgroups of
that contain it, then any isomorphism from to a Coxeter group must
take to a reflection in . The aim of this paper is to show how to
determine, by inspection of the Coxeter graph, the intersection of the maximal
finite sugroups containing . In particular we show that the condition above
is satisfied whenever is infinite and irreducible, and has the property
that all rank two parabolic subgroups are finite. So in this case all
isomorphisms map reflections to reflections.Comment: 25 pages, 0 figure
Holographic analysis of thin films
Technique for monitoring deposition of films on surfaces, in place on a real-time basis, reads both the thickness and the uniformity of the deposited film. Holograms are produced from both reflected and transmitted light on one plate
() spectroscopy using Cornell potential
The mass spectra and decay properties of heavy quarkonia are computed in
nonrelativistic quark-antiquark Cornell potential model. We have employed the
numerical solution of Schr\"odinger equation to obtain their mass spectra using
only four parameters namely quark mass (, ) and confinement strength
(, ). The spin hyperfine, spin-orbit and tensor
components of the one gluon exchange interaction are computed perturbatively to
determine the mass spectra of excited , , and states. Digamma,
digluon and dilepton decays of these mesons are computed using the model
parameters and numerical wave functions. The predicted spectroscopy and decay
properties for quarkonia are found to be consistent with available experimental
observations and results from other theoretical models. We also compute mass
spectra and life time of the meson without additional parameters. The
computed electromagnetic transition widths of heavy quarkonia and mesons
are in tune with available experimental data and other theoretical approaches
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